Sandwich panel

What are the sandwich panels

Sandwich panels, also known as composite panels or structural insulated panels, are a type of multi-layer structural cladding system that consists of two thin and strong metal sheets attached to a substantiating core material. The metal sheets are coated with a corrosion-resistant coating and the core material is usually polystyrene, polyurethane, mineral wool.

The structural functionality of a sandwich panel is similar to the classic I-beam, where two face sheets primarily resist the in-plane and lateral bending loads (similar to flanges of an I- beam), while the core material mainly resists the shear loads (similar to the web of an I-beam).[1] The idea is to use a light/soft but thick layer for the core and strong but thin layers for face sheets. This results in increasing the overall thickness of the panel, which often improves the structural attributes, like bending stiffness, and maintain or even reduce the weight.

In building and construction, these prefabricated products designed for use as building envelopes. They appear in industrial and office buildings, in clean and cold rooms and also in private houses, whether renovation or new-build. They combine a high-quality product with high flexibility regarding design. They generally have a good energy-efficiency and sustainability.

What are the advantages of sandwich panels

Sandwich panels are an increasingly popular building material that offer a number of advantages. These panels are constructed from two pieces of metal, a top layer and a bottom layer, that are connected together with an insulating core of foam or other material. Using sandwich panels for construction makes the structure stronger, more energy efficient, and provides better acoustic and thermal insulation than traditional building materials like wood and concrete.

Insulation

Sandwich panels made with core polyurethane, poly-isocyanurate foam or mineral wool Their insulation has excellent thermal insulation performance, which could be proved by comparing with other construction materials in heat transfer coefficient. The panel has high insulation properties as much as 14-80 times than brick and concrete. The panel therefore is a best choice for the use of strict control of temperature requirements.

Prevent condensation

There are two methods for building thermal insulation in general: internal thermal insulation and external thermal insulation. For internal insulation it would generate temperature difference in different divided spaces, such as indoor area and the back of small rooms, and resulting condensation normally. On the other hand, external insulation covers a building completely with insulation material; therefore the divided space between indoor area and the back of small rooms sharing stable temperature will not generate condensation. Sandwich panels adopt external insulation method which would prevent condensation effectively.

Fire Resistance

The use of fire-resistant or fire-retardant materials for the core material in the middle of the sandwich panel can stop the fire from spreading in the event of a fire. The outer “skins” of the panel are designed to resist the spread of flames. These skins are often treated with special fire-resistant materials that create a barrier between the flame and the interior of the panel. This improves fire safety and reduces the rate at which fire can spread.

Durability

Sandwich panels boast excellent strength and durability. The core is made from either Styrofoam or polyurethane foam. This foam insulation is both lightweight and incredibly strong, making it extremely capable of withstanding considerable force. It can also absorb shock, while retaining its structural integrity over extended periods of time.The prefabricated panels are made from either steel or aluminum, giving them an even greater strength. This makes sandwich panels an ideal choice for applications such as walls and roofs.

Classification of sandwich panel by function

The sandwich panels are classified according to the part of the sandwich panel, sandwich panels are divided into roof sandwich panels and wall sandwich panels.

Roof sandwich panels

Wall sandwich panels

Classification of sandwich panels by core material

Sandwich panels are composite materials used in a diverse range of construction and engineering applications. The panels are formed using two sheets of strong, thin metal (steel, stainless steel or aluminum) bonded between a core material. There are several types of core materials, including polyisocyanurate (PIR), polyurethane (PUR), expanded polystyrene (EPS), rock wool, and composite honeycomb. The core material, in combination with material strength and corrosion resistance of the metal sheets, determines the suitability of different sandwich panels for various construction applications.

Polyisocyanurate (PIR)

Polyisocyanurate (PIR) is a cured form of polyurethane, and is the most commonly used material in the production of sandwich panels. PIR is a lightweight, rigid foam that has high insulation properties and excellent fire resistance. It is also moisture-resistant and relatively low-cost due to its widespread use in the manufacture of building insulation products. PIR core panels are well-suited for uses such as roofing systems, wall insulation, and floor insulation due to their low thermal conductivity and structural stability.

Polyurethane (PUR)

Polyurethane (PUR) core panels are similar to PIR in many ways, and offer similar characteristics such as high insulation values and excellent resistance to fire. However, PUR panels are usually not as lightweight as PIR, and therefore have slightly lower insulation properties and higher costs. As such, they are more often used in situations where the additional strength and durability of PUR is necessary, such as in hi-load roofing. PUR panels are also optimal for areas where a higher initial thermal resistance (R-value) is required, as the foam is better at retaining heat.

Expanded Polystyrene (EPS)

Expanded polystyrene (EPS) is commonly used in the manufacture of insulation products, such as wall and floor insulation panels. This is because it offers excellent thermal resistance similar to PIR and PUR, but is even lighter and more cost-effective. EPS also has a high compressive strength, making it suitable for use in high-load applications such as walls and floors. Additionally, the foam does not contain medically hazardous substances, making it a popular choice for indoor applications. However, EPS is not as resistant to moisture or fire as PIR or PUR, making it less suitable for certain construction applications.

Rock wool

Rockwool is an inorganic material made from molten rocks and slag. Compared to other core materials, it is more rigid and has significantly higher thermal resistance due to its mineral composition. As a result, rock wool panels are often used in applications requiring excellent insulation, such as roofing and wall insulation. They are also approved for use as fire barriers in high-risk areas due to their superior fire resistance. However, because of their weight and brittleness, rock wool panels are not suitable for applications that require significant structural stability.

Composite Honeycomb

Composite honeycomb is a lightweight material made from more than one layer of polymer sheets and a honeycomb core. Due to its high strength and low weight, composite honeycomb is used in the construction of high-load structures such as aircraft and automobiles. The material is also very rigid and has excellent acoustic and thermal insulation properties, making it suitable for a variety of applications. However, composite honeycomb is also the most expensive of the core materials discussed, making it unsuitable for many construction applications.

In the application of sandwich panels, the core material of the panel is the main determinant of its suitability for the application, especially in terms of its thermal and acoustic insulation properties, strength and stability, fire resistance and moisture resistance. Whichever core material is chosen, it is important to carefully consider the intended application to maximize the efficiency of the sandwich panel.